The present invention relates to rotary regenerative heat transfer devices and, more particularly, to air preheaters wherein the individual heat transfer elements are stacked in open baskets which, in turn, are disposed in compartments in the rotor of the transfer device.
Air preheaters utilize the heat that would otherwise be lost out the smoke stacks of industrial and central power station boilers. In the preheater, this waste heat is captured before it reaches the stack and is transferred to the incoming cold air. Thousands of specially formed steel sheets--called heat transfer elements--absorb the waste heat from hot gases flowing through one half of the preheater structure--and release it to the incoming cold air as it passes through the other half of the structure. The heat transfer elements are spaced and arranged in a cylindrical shell called the rotor. The spaces between the elements allow the air and gas streams to flow across the surface of each sheet. The rotor revolves slowly within the preheater structure, carrying the elements alternately through the air and gas streams so that there is a continuous transfer of heat.
As a means of facilitating the efficient removal and replacement of the heat transfer elements in an air preheater, it is the common practice to stack the individual elements in baskets which are inserted into compartments formed in the rotor. To reduce both weight and cost, the element baskets most commonly comprise an open frame, rather than solid walls.
After the heat transfer device has been in service for some time, the diaphragms and stay plates which define the basket-receiving compartments may become distorted by the operating conditions to which they are exposed. To insure that the baskets may be freely inserted and removed from the compartments, despite such distortion, the baskets are generally undersized. Thus, substantial gaps exist between the baskets and the rotor compartment walls. These gaps allow a portion of the gas and air flows to bypass the heat transfer elements, resulting in a loss of thermal efficiency.
It is, therefore, a primary object of the present invention to provide an element basket for an air preheater or similar heat transfer device wherein the gas and air flows are constrained to pass substantially completely over the heat transfer elements.
It is a further object to provide such an element basket which may be readily inserted and removed from a basket-receiving compartment in the rotor.
It is yet another object to provide an element basket as aforesaid which is light in weight and inexpensive to produce.
The foregoing and other objects as may hereinafter appear are achieved by an element basket including at least one side sealing member consisting of an imperforate sheet fastened on the outside of the basket frame and substantially completely covering a side of the basket, a distal edge portion of the sheet being bent back upon itself and biasable against a wall surface of the rotor. The side sealing member fills the gaps between the element basket and the adjacent rotor compartment wall, preventing gas or cold air from bypassing the heat transfer elements in the basket.